In normal healthy skin there is an imperceptible shedding of peripheral corneocytes, to be replaced by lower level corneocytes, a process named desquamation. This occurs by the breakdown of the cohesive forces binding the peripheral corneocytes. One of the main cohesive elements is the rivet-like desmosome which is a protein complex comprising glycoproteins anchored in the membrane, responsible for corneocyte-corneocyte adhesion. To enable desquamation to occur these glycoproteins have to be degraded by the action of specific proteases.
Under certain circumstances there is an aberrant breakdown of the desmosomes in the peripheral corneocytes leading to the dry-flaky skin condition. This has been demonstrated by retention of desmosomal structures and the desmosomal glycoprotein desmoglein (dg1) in the surface layer of stratum corneum, where in normal skin these cannot be readily detected.
Walsh et al in a paper presented to the British Society of Dermatology in May 1990 have suggested that the oligosaccharide chains of the stratum corneum desmosomal glycoproteins may protect the proteins from proteolytic degradation and that prior treatment with glycosidases, to remove the sugar side chains, may be required before the proteases can breakdown the adhesive proteins.